1. Field of the Invention
This invention relates to an optical disc recording and reproducing apparatus that optically accesses the optical disc, and more particularly recording method and apparatus of a multi-rate optical disc wherein the optical disc can be adaptively driven based on a transfer rate of data to be recorded.
2. Description of the Prior Art
In a conventional optical disc recording and reproducing apparatus, light beams are irradiated onto the optical disc such as Compact Disc (CD) and Digital Versatile (or Video) disc (DVD) in order to access data. Such optical discs record binary data representing audio signals, video signals, text information, etc.
Digital signals recorded onto the optical disc and reproduced therefrom include various recording signals such as a video signal, an audio signal, digital data or a digital broadcasting program including a combination of all of said signals, etc. Each of these signals has a different data quantity, for example digital bit quantity per second, respectively. Also, in the same broadcasting program, the data quantity is different according to the attribute of a broadcasted program. Specifically, the data quantity is about 6 to 7 Mbps in the case of a sports program, whereas the data quantity is generally about 3 to 4 Mbps in the case of a movie program. Moreover, the data quantity may differ according to the number of pixels of a program being provided. Specifically, the data quantity is about 5 to 6 Mbps in the case of the existed NTST and PAL signals having an array of about 720.times.480 pixels (normal video signal hereinafter), whereas the data quantity is generally about 10 to 15 Mbps in the case of a high density signal having an array of 1024.times.1024 pixels (high resolution signal hereinafter). Optical disc apparatuses must therefore be capable of recording and reproducing digital programs having such various data quantities.
However, a conventional optical disc has only a single-rate recording means. The following is a description of an example of a conventional optical disc recording and reproducing apparatus, which records and reproduces the normal video signal of 5 Mbps and the high resolution signal of 10 Mbps to/from a conventional optical disc. The conventional optical disc recording and reproducing apparatus drives the optical disc at a transfer rate of 10 Mbps on the optical disc. Consequently, when recording the high resolution video signal of 10 Mbps in a real time, the conventional optical disc recording and reproducing apparatus can exploit the entire recording area of the optical disc, that is, 100% of recording area in the optical disc. By contrast, when recording the normal video signal of 5 Mbps in real time, the conventional optical disc recording and reproducing apparatus wastes half the record area, that is, 50% of record area in the optical disc unnecessarily. Such a conventional optical disc recording and reproducing apparatus also wastes the recording area unnecessarily when recording the audio signal and the text signal with different transfer rates.
For reference, the following describes the process in which the high resolution video signal and the normal video signals are recorded, respectively, using the optical disc recording and reproducing apparatus.
FIG. 1 is a time chart for explaining the process in which the high resolution video signal of 10 Mbps is recorded by the optical disc recording and reproducing apparatus. The frame dividing signal FDS shown in FIG. 1 assigns odd number and even number frames of the video signal. The high logic region and the low logic region of the frame dividing signal FDS represent the odd number frames and the even number frames, respectively. The high resolution video data divided into frame units according to this frame dividing signal is inputted to optical disc recording and reproducing apparatus at a rate of 10 Mbps. Then, the optical disc recording and reproducing apparatus formats the high resolution video signal HVD in a certain form required by an optical disc, and records on the optical disc. At this time, the optical disc is rotated at a constant velocity by the optical disc recording and reproducing apparatus like DSS shown in FIG. 1. As a result of this, an information pit train IPT is formed on the information track of the optical disc having frame video data pits arranged continuously, as shown in FIG. 1.
FIG. 2 is a time chart for explaining the process in which the normal resolution video signal of 5 Mbps is recorded by the optical disc recording and reproducing apparatus. In FIG. 2, the normal video data NVD are divided into frame units by the frame dividing signal FDS. This normal video data is inputted to the optical disc recording and reproducing apparatus at a transfer rate of 5 Mbps, and formatted, like FNVD in FIG. 2, by the optical disc recording and reproducing apparatus. The formatted normal video data FNVD consists of compressed frame video data and null data inserted between the compressed frame video data. These null data are generated because the normal video data NVD of 5 Mbps is temporally compressed into 1/2 by the optical disc recording and reproducing apparatus operating at a rate of 10 Mbps. In turn, the formatted normal video data FNVD are recorded on the optical disc using the optical recording and reproducing apparatus. At this time, the optical disc rotates at the same velocity used to record the high resolution video data. As a result of this, an information pit train IPT is formed on the information track of the optical disc in which video data pit regions and null data pit regions are arranged alternately.
As described above, the conventional optical disc recording and reproducing apparatus causes the null data to be recorded on optical disc because it records data on the optical disc at a fixed transfer rate, regardless of the transfer rate of data. The conventional optical disc recording and reproducing apparatus therefore wastes the recording area of the optical disc unnecessarily.